This invention relates to a process for converting well drilling cuttings that carry in or on them petroleum hydrocarbons in such a manner that the drill cuttings are converted to a product that is environmentally acceptable for spreading on the earth""s surface.
When drilling oil and gas wells into subterranean formations below the earth""s surface particles of the formation drilled through, known as drill cuttings, are formed by the drilling process. These cuttings vary in size from fines to sand size to pebble size and can carry petroleum hydrocarbons from an oil-based drilling mud used to drill the well, from petroleum hydrocarbons naturally occurring in the formations that were drilled through, or from other sources. The result is that the drill cuttings recovered at the earth""s surface carry, either internally or on their surface or both, petroleum hydrocarbons. The drill cuttings can also carry salts of various compositions but primarily alkali metal and alkaline earth metal salts that are naturally present in the formations being drilled through, in liquids in those formations, or in the drilling mud being used for the drilling process. These drill cuttings need to be disposed of in an environmentally friendly manner.
Various processes have been employed for the disposal of such drill cuttings. One such process involves stabilization of the cuttings followed by disposal of the stabilized cuttings either by burial or road spreading. In this process the cuttings are mixed with an equal weight or volume of environmentally acceptable product such as fly ash or fluidized bed coal ash which have an acceptably low metal content. Disposal of the stabilized cuttings, which are now double their original weight or volume of the original cuttings because of the stabilization process, can be carried out by, (1) burial in the earth in a single monolithic block which in some cases may include encasing the block in a plastic containment wrap, (2) spreading over a large surface area of the earth to a thickness established by current regulations, (3) spreading on an existing road surface followed with a lime-containing cap and compaction, (4) subsurface or annular injection, or (5) transportation to a commercial disposal facility.
The stabilization process, although effective, suffers from the distinct disadvantage of essentially doubling the weight and/or volume of the material, the drill cuttings, to be disposed. The various disposal methods add to this doubling disadvantage of the stabilization process disadvantages peculiar to each disposal method.
For example, burial of a plastic-wrapped monolithic block forms a large block in the earth that was not formerly present but which will now be always present and which can be the subject of required removal in the future should environmental regulations change. Accordingly, burial is an expensive means of disposal that can later become even more expensive if removal is later required, and burial does not help the portion of the earth in which it is buried to restore itself to its natural condition.
A one-time application of the cuttings to the surface of the earth to a thickness established by current regulations, e.g., less than two inches, requires a large land surface area, and can be carried out on a particular site for a limited number of applications dependent on both site and waste characteristics, thereby requiring a constant search for large and therefore expensive land areas suitable for limited disposal use.
Application to a road surface takes a large amount of road area as well. Lime-containing capping and final compaction is expensive. Like the burial of the monolithic block referred to hereinabove, it would be expensive to remove and dispose of elsewhere if later required.
Subsurface or annular injection is expensive and can involve additional environmental risks should failure or xe2x80x9cbroachxe2x80x9d occur during injection. There is also the risk of claims concerning ground water contamination, which are difficult to prove or disprove.
Transportation to commercial disposal facilities is also expensive and can involve additional environmental risks should an accident occur during transportation. There is also risk to the cuttings owner should the commercial facility be later shown not to have employed environmentally acceptable disposal processes or techniques.
Accordingly, it is highly desirable to have a process that does not double the weight or volume of the drill cuttings to be disposed of and which disposes of the drill cuttings near the drill site in an environmentally friendly manner that enhances rather than detracts from the disposal site returning to its natural condition in a reasonably short length of time.
In accordance with this invention, drill cuttings carrying petroleum hydrocarbons, water, produced water, various drill mud additives, and sometimes salts, are converted to a plant growth enhancing humus-like product without substantial increase beyond the original weight and volume of the drill cuttings themselves while at the same time reducing the total petroleum hydrocarbon content (and salt content, if any) to environmentally friendly levels.
The humus-like product of the process of this invention can be used to enhance plant growth on disturbed surface soil areas that are subject to the loss of surface solids to storm water runoff, particularly when disturbed areas are on sloping land.